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grpc-js: Simplify pick_first behavior

This commit is contained in:
Michael Lumish 2024-07-30 17:59:08 -07:00
parent f5ea6ce271
commit a6575c3e73
1 changed files with 28 additions and 38 deletions
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66
packages/grpc-js/src/load-balancer-pick-first.ts
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@ -320,21 +320,16 @@ export class PickFirstLoadBalancer implements LoadBalancer {
private removeCurrentPick() {
if (this.currentPick !== null) {
/* Unref can cause a state change, which can cause a change in the value
* of this.currentPick, so we hold a local reference to make sure that
* does not impact this function. */
const currentPick = this.currentPick;
this.currentPick = null;
currentPick.unref();
currentPick.removeConnectivityStateListener(this.subchannelStateListener);
this.currentPick.removeConnectivityStateListener(this.subchannelStateListener);
this.channelControlHelper.removeChannelzChild(
currentPick.getChannelzRef()
this.currentPick.getChannelzRef()
);
if (this.reportHealthStatus) {
currentPick.removeHealthStateWatcher(
this.pickedSubchannelHealthListener
);
}
this.currentPick.removeHealthStateWatcher(
this.pickedSubchannelHealthListener
);
// Unref last, to avoid triggering listeners
this.currentPick.unref();
this.currentPick = null;
}
}
@ -418,20 +413,25 @@ export class PickFirstLoadBalancer implements LoadBalancer {
this.connectionDelayTimeout.unref?.();
}
/**
* Declare that the specified subchannel should be used to make requests.
* This functions the same independent of whether subchannel is a member of
* this.children and whether it is equal to this.currentPick.
* Prerequisite: subchannel.getConnectivityState() === READY.
* @param subchannel
*/
private pickSubchannel(subchannel: SubchannelInterface) {
if (this.currentPick && subchannel.realSubchannelEquals(this.currentPick)) {
return;
}
trace('Pick subchannel with address ' + subchannel.getAddress());
this.stickyTransientFailureMode = false;
this.removeCurrentPick();
this.currentPick = subchannel;
/* Ref before removeCurrentPick and resetSubchannelList to avoid the
* refcount dropping to 0 during this process. */
subchannel.ref();
if (this.reportHealthStatus) {
subchannel.addHealthStateWatcher(this.pickedSubchannelHealthListener);
}
this.channelControlHelper.addChannelzChild(subchannel.getChannelzRef());
this.removeCurrentPick();
this.resetSubchannelList();
subchannel.addConnectivityStateListener(this.subchannelStateListener);
subchannel.addHealthStateWatcher(this.pickedSubchannelHealthListener);
this.currentPick = subchannel;
clearTimeout(this.connectionDelayTimeout);
this.calculateAndReportNewState();
}
@ -448,20 +448,11 @@ export class PickFirstLoadBalancer implements LoadBalancer {
private resetSubchannelList() {
for (const child of this.children) {
if (
!(
this.currentPick &&
child.subchannel.realSubchannelEquals(this.currentPick)
)
) {
/* The connectivity state listener is the same whether the subchannel
* is in the list of children or it is the currentPick, so if it is in
* both, removing it here would cause problems. In particular, that
* always happens immediately after the subchannel is picked. */
child.subchannel.removeConnectivityStateListener(
this.subchannelStateListener
);
}
/* Always remoev the connectivity state listener. If the subchannel is
getting picked, it will be re-added then. */
child.subchannel.removeConnectivityStateListener(
this.subchannelStateListener
);
/* Refs are counted independently for the children list and the
* currentPick, so we call unref whether or not the child is the
* currentPick. Channelz child references are also refcounted, so
@ -478,15 +469,13 @@ export class PickFirstLoadBalancer implements LoadBalancer {
}
private connectToAddressList(addressList: SubchannelAddress[]) {
trace('connectToAddressList([' + addressList.map(address => subchannelAddressToString(address)) + '])');
const newChildrenList = addressList.map(address => ({
subchannel: this.channelControlHelper.createSubchannel(address, {}),
hasReportedTransientFailure: false,
}));
trace('connectToAddressList([' + addressList.map(address => subchannelAddressToString(address)) + '])');
for (const { subchannel } of newChildrenList) {
if (subchannel.getConnectivityState() === ConnectivityState.READY) {
this.channelControlHelper.addChannelzChild(subchannel.getChannelzRef());
subchannel.addConnectivityStateListener(this.subchannelStateListener);
this.pickSubchannel(subchannel);
return;
}
@ -522,6 +511,7 @@ export class PickFirstLoadBalancer implements LoadBalancer {
if (!(lbConfig instanceof PickFirstLoadBalancingConfig)) {
return;
}
this.requestedResolutionSinceLastUpdate = false;
/* Previously, an update would be discarded if it was identical to the
* previous update, to minimize churn. Now the DNS resolver is
* rate-limited, so that is less of a concern. */